That was the specific personal advice he gave me at the end of spending 10 days at a retreat in nature together.

Makes sense then. He got to know you quite well, and realized that a 'direct' style would work best for you.

The idea of learning a bunch of techniques to change woman into liking you instead of working to change yourself doesn't seem to be successful.

That's not really what's happening, though. The techniques are there to change the image you're presenting and ensure that it reflects you at your best and most attractive. That's why 'the inner game' (changing yourself) and 'the outer game' (changing your social image/approach) are largely seen as complementary and mutually reinforcing.